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Homework Help: Misc. Conceptuals (Magnetism+Electric Field+ Rotational motion)

  1. Sep 16, 2009 #1
    Here are a couple of questions I'm having trouble with.

    1) Can a magnet have 3 poles?
    [Note: I've been told that a magnet might develop two north poles at the centre and two south poles at either end if it is faultily magnetised, but I'd much appreciate some explanation=)]

    2) If the current through a conductor is straight, the magnetic field it develops is circular. Explain.
    [Note: Is this because of ampere's circuital law?]

    3)In rotational motion, which of the following quantities remains fixed and why?
    a. Tangential acceleration
    b. Angular acceleration
    [Note: I dunno!]

    4)In a parallel plate capacitor, a potential of 100 volt is applied between the ends. One plate in positively charged, while the other is earthed. What will be the electric field intensity at any point between the plates?
    [Note: The intensity's supposed to be the same at any point between the plates, but how do I calculate the intensity if the distance between the plates and charge density aren't given?! But then again, does intensity depend on the distance between the plates at all? Because if it did, it WOULDN'T be the same at all points. I'm confused!]
  2. jcsd
  3. Sep 16, 2009 #2
    I can't help you without giving you the answers so i'm just going to give you the areas that you should go read back up on in one of your text books

    2)right hand rule
    3)centripetal acceleration
    if you quickly read up on these areas you'll find your answers easy
  4. Sep 16, 2009 #3
    For question 3 it is the tangential acceleration that is not constant. This acceleration is perpendicular to the force vector that points inwards towards the centre of the circle. So it is constantly changing direction as the object rotates.

    For question 4 can't you just gauss's law to calculate the field?

    [tex]\oint[/tex]E.da = [tex]\sigma[/tex]A/Eo

    Or it might be that you can use E = -[tex]\Delta[/tex]V
  5. Sep 17, 2009 #4
    Thanks! I did try looking them up before I posted, though :). Could you at least tell me if the guesses I made are correct, or on the right track? I'd much appreciate it. :) Also, the last question is freaking me out!
  6. Sep 17, 2009 #5
    Thanks, but I think Gauss is valid for closed surfaces, isn't it? If it's a parallel plate capacitor it isn't really enclosing any charge is it?
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